The present invention relates to a copier, facsimile apparatus, printer or similar image forming apparatus and more particularly to an image forming apparatus of the type causing a developing liquid to form a thin layer on a developer carrier and contact a latent image formed on an image carrier, and transferring the resulting toner image to a recording medium.
An image forming apparatus of the type described includes a developing unit for developing a latent image electrostatically formed on a photoconductive element or similar image carrier with charged toner. To miniaturize the developing unit, it has been proposed to use a dense viscous developing liquid consisting of an insulating liquid and toner dispersed in the liquid with a relatively high content. Japanese Patent Laid-Open Publication No. 7-209922, for example, teaches a developing method using a viscous developing liquid consisting of an insulating liquid and toner dispersed therein with a content as high as 100 to 10,000 mPa.multidot.S. This developing liquid is applied to a conductive developer carrier and brought into contact with an image carrier in order to develop a latent image.
Another conventional developing unit of the type using a developing liquid includes a developer carrier implemented by a flexible endless belt for applying the liquid to the image carrier. The belt is passed over and driven by a plurality of belt rollers. An applicator roller feeds the liquid from a tank to the belt in the form of a thin layer.
The problem with the above developing unit using the endless belt as a developer carrier is how the belt should be driven. When the belt is driven under tension by a plurality of belt rollers, the axes of the belt rollers must be precisely parallel to each other in order to prevent the belt from being displaced in the axial direction of the rollers. It is therefore necessary to arrange, e.g., a mechanism for adjusting the axis of each belt roller in a portion supporting the belt roller. As a result, a structure for supporting the belt and a driveline for driving the belt are complicated and expensive.
Moreover, the above developing unit needs a great number of parts including the belt rollers and is therefore bulky. Such a developing unit would increase the overall size of, e.g., a color image forming apparatus including a plurality of developing units.